This application claims the priority of the commonly owned copending German patent application Serial No. 101 33699.3 filed Jul. 11, 2001. The disclosure of the aforesaid German priority application, as well as that of each US and/or foreign patent and/or patent application identified in the specification of the present application, is incorporated herein by reference.
This invention relates to improvements in apparatus which are known as torque converters, and more particularly to improvements in fluid-operated torque converters. Still more particularly, the invention relates to improvements in fluid-operated torque converters which can be utilized with advantage in the power trains of motor vehicles, especially for controlled transmissions of torque between driving and driven parts, e.g., between the rotary output element of a prime mover (such as the camshaft or the crankshaft of an internal combustion engine) and the rotary input shaft of an automatic change-speed transmission.
An apparatus of the above outlined character normally comprises a rotary housing which is non-rotatably connected to the output element of the prime mover, a pump which is driven by and can constitute an integral part of the housing, a turbine which can be driven by the pump through the medium of a body of fluid in the housing and can transmit torque to the input shaft of the transmission, an optional stator which (if utilized) is installed in the housing between the vanes of the pump and the turbine, and a bypass clutch or lockup clutch (hereinafter called bypass clutch) which can be engaged to bypass the pump, e.g., to transmit torque directly between the housing and the turbine or the input shaft of the transmission. Such torque converters often employ at least one additional constituent which is installed between an input part and an output part and serves as a torsional vibration damper, e.g., between a (first) hub of the turbine and a (second) hub affixed to the input shaft of the transmission. In addition to performing the above-enumerated tasks, the torque converter can further serve as a starter clutch between the engine and the automatic transmission in the power train of the motor vehicle.
The bypass clutch of the torque converter is arranged to become effective during certain stages of operation of a motor vehicle, and more specifically of the torque converter, for example, when there is no need for torque conversion and/or when it is desired to avoid or reduce energy losses due to pronounced slippage between the pump and the turbine. As already mentioned above, engagement of the bypass clutch entails direct transmission of torque between the housing and the output element(s) of the torque converter, e.g., from the housing (or from a part sharing all angular movements of the housing) to a hub or another part which shares the angular movements of the input shaft of the change-speed transmission. Otherwise stated, the transmission of torque (in the at least partially engaged condition of the bypass clutch) is effected as a result of frictional engagement between one or more parts rotating with the housing and one or more parts non-rotatably connected with the input shaft of the transmission.
The just discussed frictional engagement invariably or frequently entails the generation of heat, for example, in the region(s) where the friction linings of a disc often forming part of the bypass clutch engage the adjacent friction surface or surfaces, e.g., a friction surface on the housing of the torque converter and a friction surface on the piston of the bypass clutch. The generation of heat is attributable to slippage between the friction linings and the respective friction surfaces, a slippage which is often desirable for the sake of comfort to the occupant(s) of the motor vehicle and develops when the condition of the bypass clutch is caused to change from that of full disengagement to that of complete engagement or vice versa.
In accordance with presently known proposals, heating or overheating of the bypass clutch is sought to be prevented (or its intensity reduced) by establishing a pressure differential between the contents of two plenum chambers which flank the axially movable piston of the bypass clutch and contain bodies of a suitable converter fluid (e.g., oil). One of the chambers is adjacent the turbine and the other chamber is adjacent a wall of the housing of the torque converter. The friction linings on the disc of the bypass clutch are provided with grooves which permit the fluid to flow between the two chambers when the fluid pressure in one of the chambers exceeds the pressure of fluid in the other chamber. The circulating fluid cools the parts which, in the absence of heat withdrawal, are likely or bound to be overheated.
When the pressure differential between the contents of the two chambers assumes a certain value, the cooling action of the aforedescribed conventional cooling systems for the parts of the bypass clutch (i.e., the rate of fluid flow between the chambers by way of the grooves in the friction linings of the clutch disc) depends upon several parameters, primarily upon the dimensions and/or configurations of the grooves and the wear upon the parts which are provided with and/or are adjacent to the grooves. In order to compensate for wear, the rate of fluid flow in the grooves of friction linings of the clutch disc in the bypass clutch of a conventional torque converter is selected in such a way that the intensity of cooling action in a new torque converter exceeds the requirements; this is to ensure that the cooling action is still acceptable when the wear upon the friction linings reaches or approximates the maximum permissible wear.
An object of the present invention is to provide a novel and improved fluid-operated apparatus which can be utilized as a torque converter and is constructed and assembled in such a way that the rate of fluid flow between the plenum chambers, and hence the cooling action upon its parts, is at least substantially constant during its entire useful life.
Another object of this invention is to provide a torque converter wherein the extent of wear upon the friction linings in the bypass clutch cannot influence, or cannot unduly influence, the rate of fluid flow between the chambers.
A further object of the invention is to provide a torque converter wherein the cooling of the friction surfaces provided on certain constituents of the bypass clutch remains satisfactory even when the wear upon such surfaces approximates or reaches the maximum permissible value.
An additional object of the instant invention is to provide a fluid-operated torque converter wherein the rate of fluid flow between the chambers when the torque converter is new need not exceed a value which approaches or matches an optimum value for the reasons of economy and/or of saving energy.
Still another object of this invention is to provide a novel and improved bypass clutch or lockup clutch for use in a fluid-operated torque converter.
A further object of the invention is to provide a bypass clutch wherein the heat transfer between the friction linings and the converter fluid (e.g., oil) is superior to that in presently known bypass clutches.
Another object of the invention is to provide a novel and improved friction lining for use in the bypass clutches of torque converters, especially torque converters which can be put to use in the power trains of motor vehicles.
An additional object of the invention is to provide a novel and improved method of enhancing or optimizing the exchange of heat between the fluid and the bypass clutch in the housing of a hydraulic torque converter.
Still another object of the invention is to provide a novel and improved method of controlling the flow of hydraulic fluid between the chambers in the housing of a fluid-operated torque converter.
A further object of the present invention is to provide a hydrodynamic torque converter with novel and improved means for mounting the output member of a torsional vibration damper in the converter housing on the input shaft of a change-speed transmission, particularly an automatic transmission, in the power train of a motor vehicle.
Another object of the instant invention is to provide a novel and improved modular fluid-operated torque converter.
One feature of the present invention resides in the provision of a fluid-operated apparatus (such as a hydrodynamic torque converter) for transmitting torque from a rotary output element of a driven unit (for example, from the crankshaft or camshaft of an internal combustion engine in the power train of a motor vehicle) to a coaxial input element of a driven unit (e.g., the input shaft of a change-speed transmission in the aforementioned power train). The improved apparatus comprises a hollow rotary fluid containing housing which is coaxial with and is connected to the output element of the prime mover, a pump which is connected with and is located in the housing, a turbine which is rotatable with the input element and is located in and can rotate relative to the housing, and a bypass or lockup clutch which is disposed in the housing and is engageable (entirely or in part) to connect the housing with the input element of the driven unit. The clutch includes a piston which is movable axially in and divides the interior of the housing into a plurality of chambers in the engaged condition of the clutch. A first chamber of such plurality of chambers has a fluid-admitting inlet and a second chamber has a fluid-discharging outlet. The piston is movable axially of the housing to engage the bypass clutch (either entirely or in part) in response to an increase of fluid pressure in the first chamber above the fluid pressure in the second chamber. The improved apparatus further comprises means for establishing a path for the flow of fluid between the first and second chambers (with attendant exchange of heat between the fluid and the adjacent parts) in the engaged condition of the clutch. Such path establishing means (hereinafter also called heat exchanger or heat exchanger unit) has a first friction surface which is borne by the housing and a second friction surface which is adjacent the first friction surface at least in the (partly or fully) engaged condition of the clutch and is rotatable with the input element. At least one of the friction surfaces has a continuous or composite groove which communicates with the first and second chambers, which defines a first portion of the aforementioned path and which is arranged to offer a pronounced resistance to the flow of a fluid (e.g., oil) therethrough. The path establishing means is further provided with at least one throttling orifice which defines a second portion of the path between the first and second chambers.
In accordance with a desirable feature of the invention, the at least one throttling orifice is arranged to offer to the flow of fluid therethrough a resistance which exceeds the pronounced resistance of the groove. The pronounced resistance of the groove can be between at least 2 and 10 percent of the combined resistance of the at least one groove and the at least one throttling orifice.
The at least one throttling orifice can be provided in a metallic part of the bypass clutch; such metallic part can include or constitute a portion of the housing, a friction disc of the bypass clutch or a portion of the piston of the bypass clutch.
The bypass clutch can further include a carrier (such as a friction disc) and at least one friction lining on the carrier. The at least one friction surface can be provided on the friction lining. In lieu of being provided on a friction disc, the at least one friction surface can be provided on a portion (e.g., a radially extending wall) of the housing, or on a portion of the piston of the bypass clutch. The at least one throttling orifice of the just discussed embodiment of the novel and improved path establishing means can be provided in the carrier of the bypass clutch.
The groove can constitute a circumferentially complete channel and the at least one friction surface can be provided with at least one opening which connects the groove with one of the chambers and offers a relatively small (such as negligible) resistance to the flow of fluid therethrough.
The improved apparatus can further include at least one torsional vibration damper which can be interposed in a power train between the housing and the input element of the driven unit.
The apparatus can further comprise a stator which is interposed between the pump and the turbine.
The groove of the path establishing means can include at least one section extending at least substantially circumferentially of the piston and having a first portion which communicates with the at least one throttling orifice and at least one second portion. Such path establishing means can be further provided with at least one opening which communicates with the at least one second portion of the at least one section as well as with one of the chambers and offers a negligible resistance to the flow of fluid therethrough.
The at least one friction surface can constitute an annular surface rotatable about an axis which coincides with the axis of the housing and having a portion remotest from such axis. The at least one throttling orifice can be provided in such remotest portion of the annular surface.
The at least one friction surface can be provided with a fluid intake adjacent the at least one throttling orifice; such intake can be defined or established by a stamped out portion of the path establishing means. The latter can include a friction lining and its at least one friction surface can be provided on such friction lining. The intake of the at least one friction surface can be constituted by a stamped-out portion of the friction lining. The latter can be further provided with the at least one throttling orifice and can further have a stamped-out passage which communicates with the at least one throttling orifice and preferably offers to the fluid flow a resistance constituting a small fraction of the resistance offered by the throttling orifice.
The path establishing means can comprise an annular component (such as a washer) and at least one friction lining which is borne by the annular component and is provided with the at least one friction surface. The at least one throttling orifice of such path establishing means can be provided, at least in part, in the annular component and the latter can have at least one first locating or positioning means which is in register with a second locating or positioning means in or on the at least one friction lining. Such positioning means facilitate rapid and accurate assembly of the annular component and the friction lining. At least one of the positioning means can include or constitute a notch in the annular component or in the friction lining.
In accordance with a further modification, the path establishing means comprises an annular metallic component and at least one friction lining which is borne by the annular metallic component and is provided with the at least one friction surface. The groove can include a first channel which is provided in the at least one friction surface and a second channel which communicates with the first channel by way of the at least one throttling orifices, at least in the at least partly engaged condition of the bypass clutch. The first channel can constitute a circumferentially complete substantially annular channel (e.g., a channel composed of a zig-zag shaped array of straight channel sections). Alternatively, at least the first channel can include a plurality of discrete sections (e.g., an array of substantially V-shaped sections).
The at least one surface of the path establishing means can constitute an annular surface and such path establishing means can be provided with a plurality of throttling orifices which are spaced apart from each other as seen in the circumferential direction of the annular surface.
It is also possible to provide the path establishing means with a plurality of throttling orifices which are disposed at different distances from the axis of the housing.
If the path establishing means includes an annular carrier, the latter can be installed between the aforementioned radial wall of the housing and the piston of the bypass clutch. Such path establishing means can further include first and second friction linings which are provided on the carrier (preferably in such a way that the carrier is disposed between them). The first and second friction linings respectively confront the wall of the housing and the piston of the bypass clutch, and the at least one friction surface can include first and second portions which are respectively provided on the first and second friction linings. The other friction surface has a first portion which is provided on the wall of the housing and confronts the first friction lining, and a second portion which is provided on the piston and confronts the second friction lining.
The groove of the just discussed path establishing means can include first and second portions which are respectively provided in the first and second portions of the at least one friction surface. The at least one orifice communicates with the first and second portions of the groove. If the path establishing means is provided with a plurality of first and second throttling orifices, the first orifices communicate with the first portion and the second orifices communicate with the second portion of the groove. The first orifices can alternate with the second orifices as seen in the circumferential direction of the annular carrier. A third portion of the path defined by the just discussed path establishing means can extend between the first and second throttling orifices; such third portion of the path can be defined by at least one portion of the groove.
In a further embodiment of the improved apparatus, the path establishing means includes an annular friction lining which is borne by the piston of the bypass clutch and engages the radial wall of the housing in the fully or partly engaged condition of the bypass clutch. The groove and the at least one throttling orifice are provided in the friction lining, and such path establishing means can further have at least one opening which connects the at least one throttling orifice with one of the plenum chambers. The at least one opening can be provided in one of the radially innermost and radially outermost surfaces of the friction lining or in the piston of the bypass clutch or in both. The arrangement is preferably such that the at least one opening and the at least one throttling orifice offer a major first resistance and the groove offers a minor second resistance to the flow of fluid between the plenum chambers.
It will be seen that the novel path establishing means is or can be integrated into the bypass clutch or vice versa.
If the path establishing means includes at least one friction lining, the latter can be disposed intermediate the piston of the bypass clutch and the aforementioned preferably or substantially radial wall of the housing. The piston is disposed between the wall and the turbine.
As already mentioned hereinbefore, the driven-unit the input element of which can receive torque by way of the pump or by way of the bypass clutch can constitute a change-speed transmission, preferably an automatic transmission.
A set of leaf springs can be provided to axially movably couple the piston of the bypass clutch with the housing.
Another important feature of the present invention resides in the provision of a hydrodynamic torque converter which can be utilized between the rotary output element of a prime mover and a rotary input element which is coaxial with the output element and forms part of a change-speed transmission, particularly in the power train of a motor vehicle. The improved torque converter comprises a rotary fluid containing housing which is coaxial with and is connectable the output element of the prime mover, a pump which is disposed in and is rotatable with the housing, a turbine which is disposed in the housing and is rotatable by fluid in the housing in response to rotation of the pump, and an engageable and disengageable bypass clutch which is disposed in the housing and is operable to at least temporarily connect the housing with the input element of the transmission. The bypass clutch includes a piston which is movable axially of the housing and divides the interior of the housing into at least two fluid-containing chambers in the at least partially engaged condition of the bypass clutch. A first chamber of the plurality of chambers has a fluid-admitting inlet, and a second chamber of the plurality of chambers has a fluid-discharging outlet. The clutch is engageable in response to admission of fluid into the first chamber at a pressure exceeding the fluid pressure in the second chamber with attendant axial movement of the piston in the housing. The clutch has a first friction surface which is rotatable with the housing, and a second friction surface which is rotatable with the input element and bears upon first surface in partly or fully engaged condition of the clutch.
The torque converter further comprises a torsional vibration damper which is disposed in the housing and includes an input member rotatable with the housing about the common axis of the housing and input element, at least in the at least partially engaged condition of the bypass clutch, an output member which is turnable about the aforementioned axis relative to the input member, and means (such as one or more coil springs) for yielding opposing rotation of the output member relative to the input member. Still further the torque converter comprises means for non-rotatably mounting the output member of the torsional vibration damper on the input element (such as a shaft) of the transmission; the mounting means includes a first hub which is rotatable with the turbine, a second hub which is adjacent and coaxial with the first hub and is axially movably carried by the input element of the transmission, a set of mating gears which couple the second hub for rotation with the output member of the torsional vibration damper and energy storing means (e.g., one or more diaphragm springs) for yieldably biasing the hubs against each other axially of the housing.
The torsional vibration damper can further comprise a second set of mating gears which couple the input member for rotation with the first hub. At least one of the two sets of mating gears can include gears having limited freedom of angular movement relative to each other.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved torque converter itself, however, both as to its construction and the modes of constructing, assembling and operating the same, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawing.